The pulmonary endothelium normally maintains a nonthrombogenic surface for blood and controls access of vasoactive materials to the circulation. This project will investigate effects of endothelial injury by selected peptides, proteases, and antibodies on mechanisms that contribute to the antithrombotic potential and influence the metabolism of vasoactive peptides. Human pulmonary endothelial cells in culture will be used to develop models of injury relevant to clinical conditions. Cells will be injured by melittin, thrombin, arachidonic acid, and antibody + complement. A variety of techniques will be used to determine the mechanism of injury by these membrane active agents. The studies will focus upon how arachidonic acid metabolism and synthesis of cell surface glycoconjugates influence the endothelial response to injury and how they affect normal endothelial cell functions. Morpholoic correlates will be sought through electron microscopic studies. Specific questions to be addressed are: 1) Is endothelial injury associated with release of specific glycoconjugates from the cell surface? 2) Does prostacyclin (or other prostaglandins) protect the endothelium from injury by membrane-active agents? 3) Does modulation of arachidonic acid metabolism by cell factors or pharmacologic agents affect injury? 4) Does the composition of cell-surface glycoconjugates affect sensitivity to injury or normal endothelial functions? 5) Do glycoconjugates regulate either prostaglandin synthesis or the metabolism of vasoactive peptides? We will study these problems in normal cells and in cells that are selectively modified for altered arachidonic acid metabolism or glycoconjugate synthesis. Cytotoxicity will be measured, cell adherence and the enzymatic activity of angiotensin I converting enzyme will provide indices of endothelial function. Our studies will help to define mechanisms of injury in pulmonary vascular diseases, and may contribute to understanding of thrombosis and diseases of complex etiology, such as adult respiratory distress syndrome (ARDS).